Description (Taken from the Investigator's Abstract) The Florida red time, produced by the dinoflagellate Gymnodinium breve, occurs almost annually and has adverse economic and health effects. Exposure of people to sea spray containing aerosolized G. breve causes irritation of the eyes, nose, and throat, as well as bronchoconstriction in some individuals. Brevetoxins (polyether breve toxins; PbTxs), produced by G. breve are responsible for the irritant and respiratory effects observed. There have been no systemic studies on human exposure to red tide aerosols correlating aerosol exposure characteristics with the incidence and severity of adverse symptoms. The overall objectives of the proposed study are to: 1) characterize the physical and chemical properties of environmental G. breve- containing sea spray aerosols to aid in dosimetric evaluations of human respiratory tract deposition; 2) characterize the physical and chemical properties of laboratory-generated G. breve aerosols to elucidate mechanisms of aerosol formation and transport, and give insight into the extent and products of environmental transformation; and, 3) assess personal occupational and recreational exposure of individual during pred time events in close collaboration with epidemiological studies (Project 4) to provide exposure concentration-response relationships. Information grained from these studies will aid in evaluations of human risk associated with repeated inhalation of red time aerosols.